Sea Green and Sapphire

A blog about a love of colour, addiction to fabrics and joy of crafting…

More Purple Basil Surprises


Some time ago I showed you the results of my purple basil experiments this summer. Well, that dye bath went quite a bit further and I was able to have several other experiments with it, all of which threw quite a few surprises into the process.

Given that purple basil seems to be better suited to dyeing silk than wool (wool just doesn’t seem to absorb much colour) I decided I won’t waste the dye on wool but try more experiments with silk instead. I had a dig around in my cupboards and found a cream coloured Thai silk scarf, a souvenir from a lovely holiday a long time ago. So in it went (after scouring and mordanting with alum), and after an hour of simmering, out it came very dark, almost black. As my hope had been a nice slate grey, a medium tone rather than a very dark shade, at first I kicked myself for not paying attention to dye rations and therefore for using way too much dye. Considering the scarf weighs only 45g one could have anticipated that not much dye is needed. A good lesson to learn, especially when dyeing finished items, rather than random amounts of economy wool…

But as I removed the scarf from the pot and the excess dye drained away, I realised the colour I had accidentally achieved was in fact truly beautiful, a sort of raven black: a very dark grey with a strong blue sheen or undercurrent to it.

And there were more surprises in store: as I washed the scarf, the alkalinity of the wash turned the colour into something else entirely: it was now a very dark jewel-like green, a regal green as my husband observed. It was a fantastic colour, but I wanted that raven blackish blue back so I soaked the scarf a vinegary water for a few hours.  I played around with different levels of acidity just to see how it affected the colour, and eventually, settled with a medium grey tone.

And once it dried, the grey in fact had a beautiful midnight-blue undertone and  a wonderful depth to it. The colour seems to change depending on the light, and it was very hard to capture the colour correctly on my camera, in the picture below it looks perhaps a bit lighter and bluer than it is in real life.

A Thai silk scarf, dyed midnight blue with purple basil

A Thai silk scarf, mordanted with alum and dyed mid-night blue with purple basil

Next I wanted to find out what would happen if I used the exhaust bath to dye some wool-silk blend yarn. After all, if wool gives you pale greyish green, and you get darker greys with silk, surely the result would be a nice heathery mixture of darker and lighter shades? Well, it didn’t quite work that way.

The skein I used was a mixture of 55% Blue Faced Leicester wool and 45% silk (undyed Decadence Heavy Lace yarn from the Stash Fine yarns). Unfortunately, the bit I didn’t really think through properly in advance was that the BFL wool was superwash, which absorbs colour differently compared to non-treated wool. So in the end both types of fibres absorbed the colour very strongly and I ended up with quite a darkish shade of medium grey.

As I thought this colour was a bit dull, I washed the skein and hoped it would turn a nice dark greeny grey, but no, it was still just a dull grey colour, just a little undercurrent of greenness in it. Then I tried a soak in vinegary water to try to turn it purple, but again, it wasn’t really co-operating, there was a slight change, but when dried, the colour had reverted to medium grey. And when, some time later, I photographed the skein, I noticed that in the outdoor light there was a distinct green tinge to it again, so I am now wondering if the colour shifts slightly even when dry. Obviously this is the colour it wants to be, so I left it for a moment (although I am still not too keen on it – it looks better on the picture than in real life – so I may give the skein a dip in an indigo vat next).

Another surprise dyeing result from purple basil

Another surprise dyeing result from purple basil

Even after all these experiments there was still quite a bit of dye in the bath left, so I decided to throw a bit more wool into the pot, but again there was a surprise in store. Rather than getting greenish grey, I just got plain straight-forward fawn, never the most exciting colour to get, but at least in this case there was the surprise factor, as I really don’t know why I suddenly started getting an entirely different colour compared to what had happened before. I even threw a few bits of silk fabric into the bath and they too came out more fawn than before, although it was more like a greyish fawn mixture, a bit like the colour of wood smoke. I’d love to know why this happened: was it that a particular pigment was now used up, or was it just the age of the dye bath, after all it had been stored, and occasionally simmered, for several weeks now?  I don’t know the answer to that, but I suppose it is just another reason why natural dyeing is such an endlessly fascinating subject.

fawn: a surprise result when dyeing alum-mordanted wool with purple basil

I certainly wasn’t expecting fawn…


Author: Heidi

I love colour wherever I find it, in art, photography, gardens, nature. I also love all kinds of fiber arts; spinning, dyeing, knitting, felting, sewing.

9 thoughts on “More Purple Basil Surprises

  1. Such interesting colours! Thanks for sharing them.

  2. Wow!!! What a stunning color on the silk. It makes me giddy. I just found your blog, and I am so glad I did! I have a question for you….do you mordant your silk with just alum, usually? Or CoT as well? I haven’t found a whole lot of info on specifically dyeing silk in the dye books I own. (I also have the Wild Colors book, it has been my #1 go-to as I’ve been learning.) I am preparing to dye some silk fabric for the first time to use with nuno felting. I am excited to experiment with a new fiber. Wool has been fascinating…how wool from different breeds takes color differently, and some with particular beauty and luster. Silk will be a whole new dimension. 🙂 Take care, Amanda

  3. Hi Amanda, welcome to my blog, I’m glad you found it 🙂

    yes I mordant my silk exactly the same way as wool – except I don’t use CoT at all because instead of the normal alum I use “alum formate” which is a different type of alum that doesn’t require any heat at all (so it’s a bit more eco and more convenient to use) and with that you don’t need to use CoT. I think in Wild Colour Jenny Dean mentions also using aluminium acetate for silk (the form of alum you use with cotton) so when I started experimenting with silk dyeing this summer, I asked the ladies in my spinners, weavers and dyers’ guild which form of alum they use, and they said any type will be fine, the normal wool alum or alum acetate and now I’ve discovered alum formate works ok too. So I decided to use my normal wool mordanting method with silk and it works just fine.

    This was my first year of dyeing silk and I’m completely smitten with it – I love the way silk absorbs colour, with some dyes you get a stronger colour than you’d get with wool, with others you get a lighter one, sometimes it’s completely different, so it really depends on the dye. A dye similar to purple basil that works beautifully with silk is black hollyhock, you get lovely greys with it with silk and if you mordant with copper you get greeney greys. I haven’t yet written a post about it as I have been ill for a few months, but I hope to do it soon. I wish you luck with your learning process, I’m sure it’ll be both fun and fascinating!


    • Hi Heidi, thanks for the welcome. And thanks so much for filling me in on your mordanting process. I looked into alum formate on the web and ended up seeing your article on cold mordanting with it–very interesting. I know Jenny Dean talks about cold mordanting with regular alum acetate, which I will try…going to get started today!

      I am starting a blog, which hopefully I’ll have time to keep up, and I’ll send you a link when I post about my silk dyeing results. 🙂

      I am sorry to hear youve not been feeling well, I hope the increasing light and longer days do you well. Here in Maine in the US it’s been very cold, but there is the subtle murmur of Spring getting ready to stir….

      My best,


      • Yes even the normal alum for wool (potassium aluminium sulfate)works very well without heat, although I must admit I haven’t exactly done scientific comparisons but many dyers in my guild use this method too and they all agree it works well. Before I started using alum formate, I just had a plastic bucket in the corner of my dyeing shed, and I would add some potassium alum sulfate and CoT to it, chuck the wool in the day before dyeing. I reused the same bucketful of water several times, just adding more alum each time and it worked very well.

        Once you’ve set it up, please do let me know what your blog is called, I’d love to read about your dyeing experiments!

  4. I am loving your blog and am definitely going to have to plant some more purple basil so I can try some dyeing with them. Thanks for this post, it was great.

    • Welcome to my blog, Krissie, glad you like it! 🙂 Just had a quick look at yours, and looks like we’re on a similar learning process, especially regarding washing and processing fleece.

      One word of warning about purple basil though – since then I have discovered from Pia who writes the Colour Cottage blog that colours from purple basil are not necessarily very light fast so it may fade quite easily. So it’s probably best to dye things that do not get a regular exposure to sunshine (or else can be re-dyed easily!).

  5. I know, I love it too. What I am thinking of doing is trying to wear my silk scarf regularly for the next 6 or so months, just to see how well the colour lasts in practise – I will then report if I think the colour is worth the effort or not…

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